Translating core cowl for a gas turbine engine

ABSTRACT

An example core nacelle includes a core cowl positioned adjacent to an inner duct boundary of a fan bypass passage having an associated discharge airflow cross-sectional area. The core cowl includes a translating section located aft of an exit guide vane positioned within the fan bypass passage. The translating section is moveable to vary the discharge airflow cross-sectional area.

BACKGROUND OF THE INVENTION

The present invention generally relates to a gas turbine engine, andmore particularly to a turbofan gas turbine engine having a core cowlincluding a translating section for varying a discharge airflowcross-sectional area of the gas turbine engine.

In an aircraft gas turbine engine, such as a turbofan engine, air ispressurized in a compressor, and mixed with fuel and burned in acombustor for generating hot combustion gases. The hot combustion gasesflow downstream through turbine stages that extract energy from thegases. A high pressure turbine powers the compressor, while a lowpressure turbine powers a fan section located upstream of thecompressor.

Combustion gases are discharged from the turbofan engine through a coreexhaust nozzle, and fan air is discharged through an annular fan exhaustnozzle defined at least partially by a fan nacelle surrounding the coreengine. A significant amount of propulsion thrust is provided by thepressurized fan air which is discharged through the fan exhaust nozzle.The combustion gases are discharged through the core exhaust nozzle toprovide additional thrust.

A significant amount of the air pressurized by the fan section bypassesthe engine for generating propulsion thrust in turbofan engines. Highbypass turbofans typically require large diameter fans to achieveadequate turbofan engine efficiency. Therefore, the nacelle of theturbofan engine must be large enough to support the large diameter fanof the turbofan engine. Disadvantageously, the relatively large size ofthe nacelle results in increased weight, noise and drag that may offsetthe propulsive efficiency achieved by the high bypass turbofan engine.

It is known in the field of aircraft gas turbine engines that theperformance of the turbofan engine varies during diverse flightconditions experienced by the aircraft. Typical turbofan engines aredesigned to achieve maximum performance during normal cruise operationof the aircraft. Therefore, when combined with the necessity of arelatively large nacelle size, increased noise and decreased efficiencymay be experienced by the aircraft at non-cruise operating conditionssuch as takeoff, landing, cruise maneuver and the like.

Accordingly, it is desirable to provide a reduced weight turbofan enginehaving a variable discharge airflow cross-sectional area that achievesimproved engine performance during diverse flight conditions in arelatively inexpensive and simple manner.

SUMMARY OF THE INVENTION

An example core nacelle includes a core cowl positioned adjacent to aninner duct boundary of a fan bypass passage having an associateddischarge airflow cross-sectional area. The core cowl includes atranslating section located aft of an exit guide vane positioned withinthe fan bypass passage. The translating section is moveable to vary thedischarge airflow cross-sectional area.

An example gas turbine engine system includes a fan nacelle having a fanexhaust nozzle, a core nacelle within the fan nacelle, a core cowlhaving a translating section, a sensor that produces a signalrepresenting an operability condition and a controller in communicationwith the sensor to move the translating section between a first positionand a second position. The first position includes a first dischargeairflow cross-sectional area and the second position includes a seconddischarge airflow cross-sectional area greater than the first dischargeairflow cross-sectional area. The translating section of the core cowlis moved between the first position and the second position in responseto detecting the operability condition.

An example method of controlling a discharge airflow cross-sectionalarea of a gas turbine engine includes sensing an operability conditionand selectively translating an aft section of a core cowl in response tosensing the operability condition.

The various features and advantages of this invention will becomeapparent to those skilled in the art from the following detaileddescription. The drawings that accompany the detailed description can bebriefly described as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a general perspective view of an example gas turbineengine;

FIG. 2 is a schematic view of an example gas turbine engine having acore cowl moveable between a first position and a second position;

FIG. 3 illustrates a partial perspective view of an exampleconfiguration of a core cowl disposed about an engine centerline axis;and

FIG. 4 illustrates an exploded cross-sectional view of an exampleconfiguration of the core cowl illustrated in FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, a gas turbine engine 10 suspends from an enginepylon 12 as is typical of an aircraft designed for subsonic operation.In one example, the gas turbine engine is a geared turbofan aircraftengine. The gas turbine engine includes a fan section 14, a low pressurecompressor 15, a high pressure compressor 16, a combustor 18, a highpressure turbine 20 and a low pressure turbine 22. A low speed shaft 19rotationally supports the low pressure compressor 15 and the lowpressure turbine 22 and drives the fan section 14 through a gear train23. A high speed shaft 21 rotationally supports the high pressurecompressor 16 and a high pressure turbine 20. The low speed shaft 19 andthe high speed shaft 21 rotate about a longitudinal centerline axis A ofthe gas turbine engine 10.

During operation, air is pressurized in the compressors 15, 16 and ismixed with fuel and burned in the combustor 18 for generating hotcombustion gases. The hot combustion gases flow through the high and lowpressure turbines 20, 22 which extract energy from the hot combustiongases.

The example gas turbine engine 10 is in the form of a high bypass ratio(i.e., low fan pressure ratio geared) turbofan engine mounted within afan nacelle 26, in which most of the air pressurized by the fan section14 bypasses the core engine itself for the generation of propulsionthrust. The example illustrated in FIG. 1 depicts a high bypass flowarrangement in which approximately 80% of the airflow entering the fannacelle 26 may bypass the core nacelle 28 via a fan bypass passage 27.The high bypass flow arrangement provides a significant amount of thrustfor powering the aircraft.

In one example, the bypass ratio is greater than 10 to 1, and the fansection 14 diameter is substantially larger than the diameter of the lowpressure compressor 15. The low pressure turbine 22 has a pressure ratiothat is greater than 5 to 1, in one example. The gear train 23 can beany known gear system, such as a planetary gear system with orbitingplanet gears, planetary system with non-orbiting planet gears or othertype of gear system. In the disclosed example, the gear train 23 has aconstant gear ratio. It should be understood, however, that the aboveparameters are only exemplary of a contemplated geared turbofan engine.That is, the invention is applicable to other engine architectures,including direct drive turbofans.

A fan airflow F1 is communicated within the fan bypass passage 27 and isdischarged from the engine 10 through a fan exhaust nozzle 30, definedradially between a core nacelle 28 and the fan nacelle 26. Core exhaustgases C are discharged form the core nacelle 28 through a core exhaustnozzle 32 defined between the core nacelle 28 and a tail cone 34disposed coaxially therein around the longitudinal centerline axis A ofthe gas turbine engine 10.

The fan exhaust nozzle 30 concentrically surrounds the core nacelle 28near an aftmost segment 29 of the fan nacelle 26, in this example. Inother examples, the fan exhaust nozzle 30 is located farther upstreambut aft of the fan section 14. The fan exhaust nozzle 30 defines adischarge airflow cross-sectional area 36 between the fan nacelle 26 andthe core nacelle 28 for axially discharging the fan airflow F1pressurized by the upstream fan section 14.

An exit guide vane 44 is positioned downstream of the fan section 14within the fan bypass passage 27. The exit guide vane 44 reduces theinstability of the fan airflow F1 that is communicated from the fansection 14 into the fan bypass passage 27. Stabilizing the fan airflowF1 reduces the amount of engine thrust loss experienced by the aircraft.

FIG. 2 illustrates a core cowl 38 of the gas turbine engine 10. The corecowl 38 represents an exterior flow surface of a section of the corenacelle 28. The core cowl 38 is positioned adjacent an inner ductboundary 25 of the fan bypass passage 27. The example core cowl 38includes a stationary section 40 and a translating section 42, each ofwhich is disposed circumferentially about the engine centerline axis A(see FIG. 3). In one example, the stationary section 40 of the core cowl38 is positioned forward from an exit guide vane 44. In another example,the translating section 42 of the core cowl 38 is positioned aft (i.e.,downstream) from the exit guide vane 44. The actual positioning andconfiguration of the core cowl 38 will vary depending upon designspecific parameters including, but not limited to, the size of the corenacelle and the efficiency requirements of the gas turbine engine 10.

In the illustrated example, the discharge airflow cross-sectional area36 extends between the aftmost segment 29 of the fan nacelle 26 adjacentto the fan exhaust nozzle 30 and the translating section 42 of the corecowl 38. Varying the discharge airflow cross-sectional area 36 of thegas turbine engine 10 during specific flight conditions providesimproved efficiency of a gas turbine engine 10. In one example, thedischarge airflow cross-sectional area 36 is varied by translating thetranslating section 42 of the core cowl 38 forward (i.e., upstream) fromits original position.

The translating section 42 of the cored cowl 38 is selectively movedfrom a first position X (represented by phantom lines) to a secondposition X′ (represented by solid lines) in response to detecting anoperability condition of the gas turbine engine 10, in one example. Inanother example, the translating section 42 is selectively moveablebetween a plurality of positions each having different discharge airflowcross-sectional areas.

The example translating section 42 includes a curved outer surface 43.The curved outer surface 43 defines an apex point 45 near a peak of thecurved outer surface 43. The apex point 45 moves relative to the aftmostsegment 29 of the fan nacelle 26 to vary the discharge airflowcross-sectional area as the translating section 42 is moved between thefirst position X and the second position X′.

In the illustrated example, a discharge airflow cross-sectional area 46associated with the second position X′ is greater than the dischargeairflow cross-sectional area of the first position X. In one example,the operability condition includes a takeoff condition. In anotherexample, the operability condition includes a landing condition. In yetanother example, the operability condition includes a crosswindcondition. However, the translating section 42 may be translated betweenthe first position X and the second position X′, or any other positionbetween the first position X and the second position X′, in response toany known operability condition, such as climb conditions andwindmilling conditions.

The translating section 42 is selectively moved to control the airpressure of the fan airflow F1 within the fan bypass passage 27. Forexample, positioning the translating section at the first position Xreduces the discharge airflow cross-sectional area, which restricts thefan airflow F1 and produces a pressure build-up (i.e., an increase inair pressure) within the fan bypass passage 27. Movement of thetranslating section 42 to the second position X′ increases the dischargeairflow cross-sectional area, which permits more fan airflow F1 andreduces the pressure build-up (i.e., a decrease in air pressure) withinthe fan bypass passage 27.

A sensor 52 detects the operability condition and communicates with acontroller 54 to translate the core cowl 38 between the first position Xand the second position X′ via an actuator assembly 56. Of course, thisview is highly schematic. It should be understood that the sensor 52 andthe controller 54 are programmable to detect known flight conditions.That is, the controller 54 is programmed to move the translating section42 to influence the discharge airflow cross-sectional area of the gasturbine engine 10 during varied flight conditions. A person of ordinaryskill in the art having the benefit of teachings herein will be able toprogram the controller 54 to communicate with the actuator assembly 56to translate the translating section 42 between the first position X andthe second position X′.

The distance the translating section 42 translates in response todetecting the operability condition will vary depending on designspecific parameters. The actuator assembly 56 returns the translatingsection 42 of the core cowl 38 to the first position X during normalcruise operation (e.g., a generally constant speed at generallyconstant, elevated altitude) of the aircraft. The discharge airflowcross-sectional area 46 permits an increased amount of fan airflow F1 toexit the fan exhaust nozzle 30 as compared to the discharge airflowcross-sectional area 36. Therefore, the design of the fan section 14 maybe optimized for diverse operability conditions of the aircraft.

FIG. 4 illustrates an example configuration of the core cowl 38. Theexample translating section 42 is axially translatable along an exteriorsurface 70 of the stationary section 40 of the core cowl 38 in adirection parallel to the longitudinal centerline axis A. In oneexample, the translating section 42 is moveable in an upstreamdirection.

The core cowl 38 includes a cavity 60 for storing the actuator assembly56, in this example. The cavity 60 is positioned within the structuralcasing of the core nacelle 26. In one example, the actuator assembly 56includes a ball screw. In another example, the actuator assembly 56 is alinear actuator assembly. The actuator assembly 56 may use hydraulic,electromechanical, electrical or any other power source to move thetranslating section 42 of the core cowl 38.

A leading edge 62 of the translating section 42 is aerodynamicallydesigned to minimize disturbance of the fan airflow Fl as the fanairflow F1 is communicated downstream within the fan bypass passage 27.In one example, the leading edge 62 tapers from an aft of the leadingedge 62 to the leading edge 62. Advantageously, an aerodynamic flowsurface is provided as the translating section 42 translates over theexterior surface 70 of the stationary section 40 such that flowdisturbance of the fan airflow F1 is minimized and engine operabilityand efficiency is improved.

An air seal 64 is provided near the leading edge 62 of the translatingsection 42 of the core cowl 38, in one example. In another example, anair seal (not shown) is optionally provided near a trailing edge 66 ofthe translating section 42. The air seals 64, in combination with theaerodynamic leading edge 62, reduce the disturbance of the fan airflowF1 and the fan airflow F1 is communicated through the fan bypass passage27. In addition, the air seals 64 prevent leakage of the fan airflow F1and of hot core gases within the core nacelle 28. The air seals 64 mayinclude any known sealing member.

The foregoing description shall be interpreted as illustrative and notin any limiting sense. A worker of ordinary skill in the art wouldrecognize that certain modifications would come within the scope of thisinvention. For that reason, the follow claims should be studied todetermine the true scope and content of this invention.

1-20. (canceled)
 21. A core nacelle comprising: a core cowl positionedadjacent an inner duct boundary of a fan bypass passage having anassociated discharge airflow cross-sectional area, wherein said corecowl includes at least one translating section located aft of an exitguide vane positioned within said fan bypass passage, said at least onetranslating section being selectively moveable to vary said dischargeairflow cross-sectional area; and at least one air seal near at leastone of a leading edge and a trailing edge of said at least onetranslating section to prevent leakage of a fan airflow and hot coregases within an interior of said core nacelle.
 22. The core nacelle asrecited in claim 21, wherein said discharge airflow cross-sectional areais defined between an inner surface of a fan nacelle and said core cowl.23. The core nacelle as recited in claim 21, wherein said core cowlincludes a stationary section at least partially forward of said exitguide vane.
 24. The core nacelle as recited in claim 23, wherein said atleast one translating section is at least partially slideable over anexterior surface of said stationary section.
 25. The core nacelle asrecited in claim 21, wherein said leading edge of said at least onetranslating section is tapered from aft of said leading edge to saidleading edge.
 26. The core nacelle as recited in claim 21, wherein saidtranslating section moves in an upstream direction to vary saiddischarge airflow cross-sectional area.
 27. The core nacelle as recitedin claim 21, wherein said at least one translating section includes acurved outer surface having an apex point, wherein said apex point movesrelative to an aftmost segment of a fan nacelle in response to movementof said at least one translating section.
 28. A gas turbine enginesystem, comprising: a fan nacelle defined about an axis and having a fanexhaust nozzle; a core nacelle having a core cowl including at least onetranslating section aft of an exit guide vane positioned within a fanbypass passage, wherein said at least one translating section isselectively moveable between a first position having a first dischargeairflow cross-sectional area and a second position having a seconddischarge airflow cross-sectional area greater than said first dischargeairflow cross-sectional area; a turbofan positioned within said fannacelle; a gear train that drives at least said turbofan; at least onecompressor and at least one turbine positioned downstream of saidturbofan; at least one combustor positioned between said at least onecompressor and said at least one turbine; at least one sensor thatproduces a signal representing an operability condition; and acontroller that receives said signal, wherein said controllerselectively moves said at least one translating section between saidfirst position and said second position in response to said signal. 29.The system as recited in claim 28, comprising an actuator assembly incommunication with said controller and operable to move said at leastone translating section between said first position and said secondposition.
 30. The system as recited in claim 29, wherein said actuatorassembly is mounted within a cavity of said core cowl, wherein saidactuator assembly includes at least one of a ball screw and a linearactuator assembly.
 31. The system as recited in claim 28, wherein saidat least one translating section is axially moveable between said firstposition and said second position.
 32. The system as recited in claim28, wherein said at least one translating section is axially moveablebetween a plurality of positions between said first position and saidsecond position.
 33. The system as recited in claim 28, wherein saidoperability condition includes at least one of a take-off condition, alanding condition, a cross-wind condition, a climb condition and awindmilling condition.
 34. The system as recited in claim 28, whereinsaid core cowl includes a stationary section forward of said exit guidevane, wherein said at least one translating section is at leastpartially slideable over an exterior surface of said stationary section.35. A method of controlling a discharge airflow cross-sectional area ofa gas turbine engine, comprising the steps of: (a) sensing anoperability condition; and (b) selectively translating an aft section ofa core cowl having at least one air seal positioned near at least one ofa leading edge and a trailing edge of said aft section in response tosensing the operability condition to control the discharge airflowcross-sectional area.
 36. The method as recited in claim 35, wherein theoperability condition includes at least one of a take-off condition, aclimb condition, a landing condition, a cross-wind condition and awindmilling condition.
 37. The method as recited in claim 35, whereinthe aft section of the core cowl is selectively moveable between a firstposition having a first discharge airflow cross-sectional area and asecond position having a second discharge airflow cross-sectional areagreater than the first discharge airflow area, wherein said step (b)comprises: translating the aft section of the core cowl from the firstposition to the second position in response to sensing the operabilitycondition.
 38. The method as recited in claim 37, comprising the stepof: (c) returning the aft section of the core cowl to the first positionin response to detection of a cruise operation.
 39. The method asrecited in claim 35, wherein the core cowl includes a stationary sectionpositioned upstream from the aft section of the core cowl and said step(b) comprises: sliding the aft section of the core cowl along anexterior surface of the stationary section.